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-rw-r--r--kernel/utsname_sysctl.c145
1 files changed, 145 insertions, 0 deletions
diff --git a/kernel/utsname_sysctl.c b/kernel/utsname_sysctl.c
new file mode 100644
index 0000000000..019e3a1566
--- /dev/null
+++ b/kernel/utsname_sysctl.c
@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2007
+ *
+ * Author: Eric Biederman <ebiederm@xmision.com>
+ */
+
+#include <linux/export.h>
+#include <linux/uts.h>
+#include <linux/utsname.h>
+#include <linux/random.h>
+#include <linux/sysctl.h>
+#include <linux/wait.h>
+#include <linux/rwsem.h>
+
+#ifdef CONFIG_PROC_SYSCTL
+
+static void *get_uts(struct ctl_table *table)
+{
+ char *which = table->data;
+ struct uts_namespace *uts_ns;
+
+ uts_ns = current->nsproxy->uts_ns;
+ which = (which - (char *)&init_uts_ns) + (char *)uts_ns;
+
+ return which;
+}
+
+/*
+ * Special case of dostring for the UTS structure. This has locks
+ * to observe. Should this be in kernel/sys.c ????
+ */
+static int proc_do_uts_string(struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct ctl_table uts_table;
+ int r;
+ char tmp_data[__NEW_UTS_LEN + 1];
+
+ memcpy(&uts_table, table, sizeof(uts_table));
+ uts_table.data = tmp_data;
+
+ /*
+ * Buffer the value in tmp_data so that proc_dostring() can be called
+ * without holding any locks.
+ * We also need to read the original value in the write==1 case to
+ * support partial writes.
+ */
+ down_read(&uts_sem);
+ memcpy(tmp_data, get_uts(table), sizeof(tmp_data));
+ up_read(&uts_sem);
+ r = proc_dostring(&uts_table, write, buffer, lenp, ppos);
+
+ if (write) {
+ /*
+ * Write back the new value.
+ * Note that, since we dropped uts_sem, the result can
+ * theoretically be incorrect if there are two parallel writes
+ * at non-zero offsets to the same sysctl.
+ */
+ add_device_randomness(tmp_data, sizeof(tmp_data));
+ down_write(&uts_sem);
+ memcpy(get_uts(table), tmp_data, sizeof(tmp_data));
+ up_write(&uts_sem);
+ proc_sys_poll_notify(table->poll);
+ }
+
+ return r;
+}
+#else
+#define proc_do_uts_string NULL
+#endif
+
+static DEFINE_CTL_TABLE_POLL(hostname_poll);
+static DEFINE_CTL_TABLE_POLL(domainname_poll);
+
+// Note: update 'enum uts_proc' to match any changes to this table
+static struct ctl_table uts_kern_table[] = {
+ {
+ .procname = "arch",
+ .data = init_uts_ns.name.machine,
+ .maxlen = sizeof(init_uts_ns.name.machine),
+ .mode = 0444,
+ .proc_handler = proc_do_uts_string,
+ },
+ {
+ .procname = "ostype",
+ .data = init_uts_ns.name.sysname,
+ .maxlen = sizeof(init_uts_ns.name.sysname),
+ .mode = 0444,
+ .proc_handler = proc_do_uts_string,
+ },
+ {
+ .procname = "osrelease",
+ .data = init_uts_ns.name.release,
+ .maxlen = sizeof(init_uts_ns.name.release),
+ .mode = 0444,
+ .proc_handler = proc_do_uts_string,
+ },
+ {
+ .procname = "version",
+ .data = init_uts_ns.name.version,
+ .maxlen = sizeof(init_uts_ns.name.version),
+ .mode = 0444,
+ .proc_handler = proc_do_uts_string,
+ },
+ {
+ .procname = "hostname",
+ .data = init_uts_ns.name.nodename,
+ .maxlen = sizeof(init_uts_ns.name.nodename),
+ .mode = 0644,
+ .proc_handler = proc_do_uts_string,
+ .poll = &hostname_poll,
+ },
+ {
+ .procname = "domainname",
+ .data = init_uts_ns.name.domainname,
+ .maxlen = sizeof(init_uts_ns.name.domainname),
+ .mode = 0644,
+ .proc_handler = proc_do_uts_string,
+ .poll = &domainname_poll,
+ },
+ {}
+};
+
+#ifdef CONFIG_PROC_SYSCTL
+/*
+ * Notify userspace about a change in a certain entry of uts_kern_table,
+ * identified by the parameter proc.
+ */
+void uts_proc_notify(enum uts_proc proc)
+{
+ struct ctl_table *table = &uts_kern_table[proc];
+
+ proc_sys_poll_notify(table->poll);
+}
+#endif
+
+static int __init utsname_sysctl_init(void)
+{
+ register_sysctl("kernel", uts_kern_table);
+ return 0;
+}
+
+device_initcall(utsname_sysctl_init);